1. Technical Field of the Invention
The present invention relates to fine metallic particles-containing fibers and a method for producing the same. The incorporation of fine particles of metals and/or hardly-soluble metallic salts into fibers can make the fibers have various functions intrinsic to such fine metallic particles, such as antibacterial property, antifungal property, odor-repelling property, deodorizing property, flame-retarding property, ultraviolet-preventing property, heat-retaining property, surface-improving property, designed property, refreshing property, electroconductive property, rust-preventing property, lubricative property, magnetic property, light-reflecting property, selectively light-absorbing property, heat-absorbing property, heat-conductive property, and heat-reflecting property. Therefore, the fine metallic particles-containing fibers with such functions can be used in various fields.
2. Prior Art
Fibers with various functions have heretofore been proposed, which contain fine metallic particles having particle sizes of not larger than micron orders or so in fiber matrices. The most popular are fine metallic particles-containing fibers to be obtained by adding and dispersing fine metallic particles themselves in a polymer followed by making the resulting polymer fibrous, such as those disclosed in Japanese Patent Application Laid-Open Nos. 1-96244, 2-16940 and 6-293611. Also known are fine metallic particles-containing fibers to be obtained by making fine inorganic particles carry fine metallic particles thereon, adding the resulting fine inorganic particles to a resin, and shaping the resulting resin, such as those disclosed in Japanese Patent Application Laid-Open Nos. 7-165519 and 7-173392. However, in such conventional, fine metallic particles-containing fibers to be obtained according to the known methods, it is difficult to uniformly disperse the fine metallic particles or the inorganic particles in the polymer since the specific gravity of the metallic particles or the inorganic particles differs from that of the polymer, since the affinity of the particles for the polymer is poor. In addition, the methods are still problematic in that, of the fine metallic particles to be added in them, finer metallic particles of not larger than sub-micron orders are difficult to prepare, that the cost of such finer particles is high, and that it is difficult to safely handle such finer particles. For these reasons, therefore, the particle sizes of fine metallic particles capable of being actually used in industrial plants are limited. Moreover, there is still another problem with the known methods in that the fibers shall frequently experience a heat history in the shaping and processing steps, in which the metals themselves in the fibers are often deteriorated.
In Japanese Patent Application Laid-Open Nos. 6-287355 and 6-293611, disclosed are shaped articles such as fibers to be produced by incorporating a metallic salt or the like into a polymer matrix, then reducing the metallic salt through heat-treatment of the polymer to thereby give a resin containing ultra-fine particles as uniformly dispersed therein, and finally shaping the resin. However, this method is problematic in that (1) there is a probability that the metallic complex or metallic salt is not uniformly dispersed in the polymer matrix during the step of mixing them, (2) the cost of the metallic complex or metallic salt to be used is high, (3) the ligand of the metallic complex used or the compound having a counter ion to the metal ion of the metallic salt used becomes unnecessary after the conversion of the metallic complex or the metallic salt into fine metallic particles, and such unnecessary substances, as often dissolving out of the final product, have some negative influences on the basic physical properties and other properties of the final product, (4) since the final product shall contain a large amount of the ligand of the metallic complex used or the compound having a counter ion to the metal ion of the metallic salt used, which becomes unnecessary after the precipitation of fine metallic particles, it is impossible to increase the content of the fine metallic particles in the final product, and (5) since the matrix to be used in the conventional techniques as referred to hereinabove is a thermoplastic resin capable of being shaped and processed under heat, the final product to be obtained could not have high heat resistance.
In Japanese Patent Application Laid-Open No. 56-148965, disclosed are fine silver particles-containing fibers in which metal silver is in the surface layer of each fiber. However, this prior art technique disclosed is also problematic in that (1) since a carboxylic acid is localized in the smallest possible area in the surface layer of each fiber in order to prevent the physical properties of the fibers from being deteriorated, the amount of the polar group capable of carrying the metal is reduced with the result that the amount of the fine metallic particles to be in the fibers is limited, and (2) since fibers that are generally obtainable in ordinary industrial plants have a thickness of about 10.mu. or more and therefore have a small surface area relative to the unit weight, their efficiency of expressing the functions of the fine metallic particles contained therein is low, and in addition, the fine metallic particles existing in the inside of the fibers but not on their surfaces could not be utilized effectively. For these problematic reasons (1) and (2), if the functions of metals are desired to be effectively utilized or, for example, if a large amount of a metal is desired to be incorporated into fibers in order to make the fibers anti-fungal, the amount of the fine metallic particles-containing fibers themselves to be mixed with other fibers must be increased, resulting in the increase in the cost of the mixed fibers. Moreover, since the amount itself of the metal existing in the fibers is not satisfactorily large, the fibers could not often express the intended functions. In addition to these (1) and (2), the prior art technique disclosed is still further problematic in that (3) since the fine metallic particles are localized only in the surface area of each fiber, the fine metallic fibers are dropped off, when the fibers are mechanically abraded, for example, in the post-processing step, thereby resulting in significant reduction in the functions of the fibers, though such is not so much problematic if the post-processing step is conducted under relatively mild conditions, and (4) since the ion-exchanged silver ion is once precipitated in the form of a silver compound and thereafter the compound is reduced, the silver compound precipitated is often removed out of the system, resulting in the reduction in the utilization of the silver ions, and in addition, the two-step reaction is troublesome and expensive.
On the other hand, with the recent diversification in the life style and with the recent increase in the density of the living environment and also the recent increase in the airtight condition in the living environment, odors have become considered problematic in the living environment and the demand for removing odors from the living environment is increasing.
Some conventional deodorizing fibers are known, for example, activated charcoal-containing fibers, and also fibers with a deodorizing substance as adhered to and fixed on their surfaces or kneaded into the fibers by post-treatment, which, however, are all problematic. Precisely, since activated charcoal-containing fibers are black and, in addition, basically have low physical properties, their use is limited. The fibers with a deodorizing substance as adhered to and fixed on their surfaces by post-treatment could not basically have large deodorizing capacity. The fibers with a deodorizing substance as kneaded thereinto by post-treatment are problematic in that, if the particles of the deodorizing substance as kneaded into the fibers have large particle sizes, they greatly worsen the physical properties of the fibers. Therefore, in the deodorizing substance-kneaded fibers, the particles of the deodorizing substance are desired to have small particle sizes. In these, in addition, it is desired that the particles of the deodorizing substance have the smallest possible particle sizes also in view of the deodorizing capacity of the fibers. However, since the particles of the deodorizing substance to be kneaded into fibers are limited in reducing their particle sizes, the deodorizing substance-kneaded fibers are still problematic in that they could not sufficiently express the deodorizing effect of the substance.